Steven Robbins

Shoe Sole Thickness and Hardness Influence Balance in Older Men

To test the hypothesis that shoes with thick, soft midsoles, such as modern running shoes, provide better stability in older individuals than those with thin‐hard midsoles. In addition, we examined the relation between footwear comfort and stability and stability when barefoot.

Running-related injury prevention through innate impact-moderating behavior.

The purpose of these experiments was to test the Robbins and Hanna hypothesis, which relates differences in discomfort from localized deformation at certain positions on the plantar surface to protective behavior (intrinsic foot shock absorption). A penetrometer was used to quantify the relations between localized load and pain and between load and depth of deformation. The magnitude of load required to elicit pain varied significantly (P less than 0.005) in relation to position on the plantar surface. With a load of 9 kg and a 10 mm spherical end on the penetrometer, 6% of the sample reported pain at the heelpad, 32% at the distal first digit, and 66% at the first metatarsal-phalangeal joint. This pattern was predicted by the Robbins and Hanna thesis. Two deformation patterns were observed which were best explained by deformation constraint by tight trabecular tethering of the epithelial membrane at the heelpad and distal first digit and unrestricted deformation due to loose trabecular tethering of the epithelial membrane at the first metatarsal-phalangeal joint. These data provide insight into how, when barefoot, the plantar surface resists perforation yet provides protection to local bony structures. These data further support the notion that plantar sensory feedback plays a central role in safe and effective locomotion.

Overload protection: avoidance response to heavy plantar surface loading.

Current footwear which are designed for use in running are examples of intentional biomechanical model integration into device design. The inadequacy of this footwear in protecting against injury is postulated to be due to fixation on inadequate models of locomotory biomechanics that do not provide for feedback control; in particular, an hypothesized plantar surface sensory-mediated feedback control system, which imparts overload protection during locomotion. A heuristic approach was used to identify the hypothesized system. A random series of loads (0 to 164 kg) was applied to the knee flexed at 90 degrees. In this testing system, plantar surface avoidance behavior was the difference between the sum of the leg weight and the load applied to the knee, and the load measured at the plantar surface; this was produced by activation of hip flexors. Significant avoidance behavior was found in all of the subjects (P less than 0.001). On all surfaces tested, including modern athletic footwear (P less than 0.001), its magnitude increased directly in relation to the load applied to the knee (P less than 0.001). There were significant differences in avoidance behavior in relation to the weight-bearing surfaces tested (P less than 0.05). With the identification of a feedback control system which would serve to moderate loading during locomotion, an explanation is provided as to why current athletic footwear do not protect and may be injurious; thus allowing the design of footwear which may be truly protective.

Protective Sensation of the Plantar Aspect of the Foot

The scientific literature suggests that barefoot activity may be beneficial. There is a current trend in recreational barefoot activity in children and adults, and barefoot running among athletes. Although the type of skin over most of the body (hairy skin) seems to be easily injured by painful abrading loads, little is known about protection provided by plantar sensory feedback against damage from excessive wear during barefoot locomotion. To evaluate this, we administered a volley of 35 painful abrading loads to glabrous and hairy skin sites over a 5-min period, and examined its effects for signs of cutaneous injury in a sample of 12 normally shod healthy male subjects. Compared with hairy skin of the thigh, plantar skin required approximately 600% greater abrading loads to reach pain threshold. Furthermore, painful stimulation produced visible redness and hypersensitivity in all subjects at the hairy skin site 24 hr after stimulation, whereas only 8.3% reported hypersensitivity and none showed erythema at the plantar area 1 day later. We found that plantar skin possesses a higher pain threshold to abrading stimuli than hairy skin. In fact, loading of the plantar area was limited to innocuous levels due to intolerable pain. We conclude that plantar skin is well protected through sensory feedback from abrasive injuries when barefoot. This information combined with previous reports suggests that risk of injury when normally shod individuals perform barefoot locomotion should be low.

Evenwicht en verticale landingskracht bij sport: de rol van schoenzoolmateriaal

Doel. Sportschoenen en matten vormen steunoppervlakken tussen voet en ondergrond. Ze zijn samengesteld uit relatief zachte, samenpersbare materialen die zijn ontworpen ter bescherming tegen letsels die kunnen optreden bij sport door de kracht van de verticale inwerking. Die landingskracht blijft ook bij gebruik van dat materiaal hoog omdat blijkt dat men daarmee harder neerkomt.